Add an exceptions.xml file in WEB-INF that provides mappings to actions:
<exception class="java.lang.IllegalStateException" action="#
<exception class="java.lang.Throwable" view-id="/error.jsp"/>
Only the most-specific action for an exception type would be invoked.
Not sure how easy it is to implement this right now, since apparently JSF nastily swallows/wraps some exceptions. Need to investigate. (Perhaps what the action around the EJBs, not the JSF lifecycle.)